What is AMR (Adaptive multi rate)?

AMR is Adaptive Multi-Rate Algorithm is a speech coding standard operating at eight-bit rates and in the range of 4.75 to 12.2 kbps. This algorithm was designed to have robustness in the link. This was developed for GSM standards. It supports dynamic adaptations to network conditions using lower bit rates during network congestion or degradation of the network while preserving the audio quality. AMR can be considered to be the most widely used codec in the world today. It is used in many applications like Digital telephony, multimedia, voice mail, test and measurement equipment, media players, media servers, content creation tools, etc.